Aluminum to copper connection



Jan. 13, 1959 L. A. COOK ALUMINUM T0 COPPER CONNECTION 2 Sheets-Sheet 1 Filed Jan. 5, 1954 FIG. 2.

INVENTOR. v LLOYD 5. COOK 6 BTTQWEY Jan. 13, 1959 L. A. COOK 2,868,863

ALUMINUM TO COPPER CONNECTION Filed Jan. 5. 1954 2 Sheets-Sheet 2 FIG. 5.

INVENT LLOYD )Q. COO

United States Patent ALUMINUM T CQPPER CONNECTION Lloyd A. Cook, Opportunity, Wasln, assignor to Kaiser Aluminum & Chemical Corporation, Oakland, Callfi, a corporation of Delaware Application January 5, 1954, Serial No. 402,287 Claims. (Cl. 174-94) This invention relates to electrical connections between two conductors of dissimilar metals. More particularly, this invention relates to a novel connector for making electrical connections between aluminum and copper conductors and to electrical connections utilizing such connector.

The increased use of aluminum conductors, particularly in the distribution field, has posed a serious problem regarding suitable connectors. To meet the demand, use has been made, in many instances, of connectors specifically designed for application to copper conductors.

In a great many cases these connectors have not proven satisfactory for the purpose intended, principally because the physical characteristics of aluminum metal as used in conductor diflers appreciably from copper and the fact that a junction between these two metals posed problems not anticipated. For example, the yield strength of a typical hard drawn aluminum conductor is approximately one-half of that of hard drawn copper conductor of the same size. Consequently, when tightening a conventional copper body clamp over an aluminum conductor, pressures may be easily developed which are beyond the yield strength of the aluminum causing the metal to flow out in a permanent deformation. Therefore, the maximum clamping pressure which can be used is governed by the relatively low yield strength of the aluminum. The thermal coefficient of expansion of the aluminum conductor is about percent greater than that of copper. Consequently, when the conventional connector for copper is heated under load, the aluminum will expand at a much faster rate than the copper with the result that the mechanical pressure on the aluminum conductor will increase rapidly until its yield strength is reached after which the aluminum will flow out in permanent deformation. When the load is subsequently released, the connector cools, but as a consequence of the flow-out,

th aluminum conductor is somewhat smaller in crosssection than prior to heating-up. This creep or metal flow during heat cycling may continue until the electrical contact is so poor that the PR losses introduced appreciably contribute to the heating of the connector and ultimately may result in burning up of the connector or melting off of the aluminum conductor.

It is also known that there exists a difference of po tential, in the electrornotive series of metals in solution, of about 2 volts between aluminum and copper, the aluminum being anodic. In the presence of an ionizable salt in solution, a bimetal electrolytic cell is set up in which current flows from the aluminum anode, through the electrolyte to the copper cathode and then returns via a metallic circuit. Such galvanic action causes aluminum metal to enter solution so long as the electrolytic current flows. The problem is further complicated by the build-up of decomposition products and the evolution of gases at the electrodes. The ultimate result of this form of electrolysis is to destroy the aluminum conductor at the regions of galvanic action.

Various connector constructions have been proposed to 8 eliminate one or more of these problems involved in aluminum to copper connections but for one or more reasons have not proved to be completely satisfactory. Accordingly, it is the primary purpose and object of this invention to provide a novel connector for making electrical connections between aluminum and copper members which eliminates or substantially reduces the disadvantages of electrical connectors as heretofore known.

Another object of this invention is to provide a novel connector which overcomes many of the problems existing in the use of prior known connectors due to dissimilar physical characteristics of aluminum and copper.

Another object of the invention is to provide anovel connector which is characterized by being light, simple, inexpensive, and one which can be readily applied to both the aluminum and copper conductors for joining the two in current carrying relationship.

Another object or the invention is to provide a novel connector for aluminum and copper conductors which substantially eliminates electrochemical corrosion which occurs when aluminum and copper are in contact in the presence of an electrolyte.

A more specific object of the invention is to provide a novel connector for aluminum and copper conductors wherein the connector is provided with an adherent layer of material to exclude moisture or condensation which would serve as an electrolyte between aluminum and copper and wherein the layer possesses a shape such that the greatest transverse dimension thereof is located inter mediate the ends of the layer and longitudinally of the connector.

Another object of the invention is to provide a novel electrical connection between aluminum and copper conductors which eliminates or substantially reduces the disadvantages of connections as heretofore known.

Other objects and advantages of the invention will be apparent from the following detailed description thereof taken in conjunction With the accompanying drawing in which:

Figure l is a side View in section of one form of the electrical connector of the invention,

Figure 2 is a side view in section of the electrical connector of Figure l forming an electrical connection between the conductors,

Figure 3 to 6 are side views in section of connectors which are modifications of that illustrated in Figure 1, and I a Figure 7 is a side View in section of the electrical connector of Figure 6 forming an electrical connection between conductors.

As shown in Figure 1, the connector generally comprises an aluminum open-ended tubular member 1 and a copper open-ended tubular member 2. Member 1 may be composed of EC (electrical conductor) grade aluminum or other suitable aluminum metal such as well known 28 or 38 alloy and member 2 may be composed of HC (high conductivity) grade copper. Members 1 and 2 are securely attached together in end to end or end opposing relationship by means of a copper insert 3 which separates the interior spaces 1 and 2' defined by members 31 and 2, respectively, and acts as a barrier against the passage of moisture therethrough and from contact of the conductors to be received in spaces 1' and 2'. Since the conductivity of the aluminum conductor which will be aflixed to member 1 is less than that of the copper conductor which will be affixed to member 2, the aluminum conductor necessarily will be larger than the copper conductor and, accordingly, insert 3 is provided with an enlarged portion 4 for attachment to member 1 and a reduced portion 5 for attachment to member 2. The dimensions of insert 3 are such that the enlarged portion 4 is disposed in the end of member 1 in a press fit and, likewise, reduced portion is disposed in the end of member 2 in a press fit. Thereafter, the opposing ends of members 1 and 2 are securely attached to insert 3 by means such as indentations (crimps) or pressure welding such that the ends of members 1 and 2 are in intimate or tight contact with insert 3 around the periphery thereof. When pressure welding is the manner of attachment, care should be exercised such that the maximum temperature existing at the interface between the copper insert 3 and aluminum member 1 avoids the formation of brittle copper-aluminum compound which would decrease the tensile strength of the connector.

Prior to attachment of the insert to members 1 and 2, the face or end of the enlarged portion 4 of insert 3, which defines one surface of space 1, is provided with an adherent coating 6 of aluminous material (aluminum or suitable aluminum base alloy).

Coating 6 may be applied by dipping the face of insert portion 4 in a. molten bath of aluminum or aluminum base alloy. When member 1 is attached-to insert portion 4 it is in contact with the edge of aluminous coating 6. Such coating ensures against the possibility of exposed contact between the aluminum conductor which will be provided in space 1 and the copper insert and resulting galvanic cell corrosion.

The external surface portions of the opposed ends of embers 1 and 2 are provided with an adherent layer 7 of a suitable material which is stable, non-conducting and moisture-resistant. Layer 7 covers at least the exposed external surface area of members 1 and 2 where the members are in closest relationship, thereby preventing the occurrence of galvanic cell corrosion in this area. Examples of suitable materials are synthetic rubbers such as neoprene or silicone. By stable is meant that the material of the layer or seal 7 possesses good resistance to the action of such things as sunlight, moisture, oxidation, solvents and heat. To ensure effective bonding between rubber-like materials such as neoprene, silicone, etc., and aluminum and copper, particularly aluminum, it is desirable to provide the exposed external surface portions of the aluminum and copper members over which layer '7 will extend, with a relatively thin coating of a suitable non-conducting and moisture-resistant adhesive or cement material 8. For example, where neoprene (polychloroprene) is the material of layer 7, which is cured and pressure molded about the members, a suitable adhesive coating 8 is Ty-Ply S, produced by the Marbon Corporation. Ty-Ply S is a rubber derivative and is a black, viscous liquid which dries to a non-tacky film. Other commonly known cement materials for bonding synthetic rubber materials to metal are Dupont MDL-SO (methylene bis 4 phenyl isocyanate in orthodichlorobenzene), TBostik 1020 and Thixon NM. The coating of cement or adhesive can be applied by any suitable means such as brushing or spraying.

The effectiveness of the bond between layer 7 and the connector members may be enhanced by means other than the use of an adhesive coating, as by wire brushing of the metal surface, caustic etch, or provision of a chemical conversion coating. An example of a suitable chemical coating is commonly known as Alodine and is produced by subjecting the metal surface to contact with an aqueous acid solution containing phosphate ions, fluoride ions, and dichromate ions, e. g. 64 grams of phosphoric acid (75%), 5 grams of sodium fluoride, l0 grams of chromic acid (CrO balance water to make one liter. The treatment may be performed by immersing the surfaces to be coated in the solution, by flowing or spraying the solution upon the work, or by other convenient techniques in which the solution is allowed to act upon the work. It is to be understood, according to the invention, that whether or not the externally exposed end surface portions of members 1 and 2 are subjected to a pretreatment as by surface roughening, providing a chemical coating or providing an adhesive coating,.the

essential requirement is that the layer 7 be very adherent to the metal surfaces such that moisture is excluded from the exposed external surface area of the members where they are in the closest relationship to thereby prevent galvanic cell corrosion in this area.

Figure 2 of the drawing illustrates the connector of Figure 1 after application to a distribution line wherein one end of the aluminum conductor 9 has been connected to the aluminum member 1 of the connector and one end of the copper conductor 10 has been connected to the copper member 2 of the connector. Although conductors 9 and 10 have been shown as solid, it is to be understood that either or both may be stranded conductors and, in the case of a stranded aluminum conductor, it may be of the ACSR type (aluminum cable steel reinforced). The conductors may be joined to connector members 1 and 2 by conventional soldering, clamping or indenting (crimping) means, Figure 2 showing the members 1 and 2 as being joined to the conductors by means of a plurality of indentations or 'crimps 11 which may be applied with a suitable tool. In use of an electrical connection as shown in Figure 2, substantially all of the current flows from one conductor to its respective connector member, through the insert to the second connector member and then to the other conductor.

Prior to inserting the ends of the conductors in the opposite ends of the connector, it is desirable to deposit in spaces 1 and 2 a suitable sealing and contact paste 12. One such material is Penetrox A which is a petrolatum base substance containing an anti-oxidant and small particles of zinc. After depositing a predetermined amount of sealing and contact paste in the aluminum and copper connector members 1 and 2, the ends of conductors 9 and 10 are placed therein and members 1 and 2 are crimped into tight engagement with the conductors. The sealing and contact paste fills any space left between the conductor ends and their respective crimped connector member to thereby not only exclude the-presence of air and moisture in the connection but to ensure satisfactory electrical contact between the conductor ends and the connector. Alternatively, the sealing and contact paste may be applied to the end portions of the conductors rather than in the connector spaces 1' and 2. While it is highly desirable to utilize such sealing and contact paste in the case of securing the aluminum conductor to .the connector, to ensure against entrapment of moisture between the metal surfaces of the aluminum connector memher and the aluminum conductor and resultant corrosion in the form of oxide formation, it is not necessary that this be done in the case of the copper conductor although it is the preferred practice.

Although the protective seal or layer 7 may take various shapes, it is preferred that layer 7 be substantially spherical or, in any case, possess a shape wherein the thickness of the layer in any given plane along the axis of the connector is not constant over the length thereof. In other words, the shape of the layer should be such that the greatest thickness thereof is located intermediate the ends of the layer, which ends form the extremities of the layer along the length of the portion of the connector which 'is covered thereby. Preferably the layer thickness in a plane perpendicular to the longitudinal axis of the memhers is substantially equal radially of the connector. Rather than a ball or sphere-like layer as shown in Figures 1 to 7, use could be made of numerous other configurations.

One of the advantages of providing a layer having a shape or configuration as set forth above is to form a barrier against and prevent any copper salts which might form at the copper end of the electrical connection from running down over the connector and initiating galvanic corrosion of the aluminum portions of the connection in cases Where the aluminum end of the connection is at a level substantially lower than the copper end thereof.

Any moisture which contacts the layer will tend to move to the lowest part thereof and drop off. Also, material of the layer is preferably selected such that it is hydrophobic. A layer or seal in the shape of a ball also possesses the advantage that it is the least easily torn or abraded form, inasmuch as it is more difficult to stretch or deform an equiaxed structure than an elongated, fiattened or angular shaped structure. Moreover, the path through a ball layer is just as great from its girth to the externally exposed opposing end surface portions in closest relationship of members 1 and 2 as it is from the extent thereof along the longitudinal axis of the connector away from the opposing end surface portions thereby giving equal protection against the atmosphere in all directions.

Figure 3 illustrates one modification of the connector of Figure 1 wherein tubular members 1 and 2 are attached in end-to-end or end-opposed relationship by means of soldering or brazing to insert 3. In the case of either soldering or brazing the insert need not be dimensioned such that it makes a press fit with the ends of members 1 and 2. Moreover, it is not necessary that the face of enlarged portion 4 of the insert 3 be aluminized. In this modification, a suitable solder metal or brazing alloy in the form of wire, e. g. ring, and of a predetermined size is positioned within members 1 and 2 and against the ends of the insert. Preferably the size of the ring is such that it is necessary to press it into place thereby holding it against movement during the subsequent heating operation. Thereafter, this assembly is heated to cause the soldering or brazing metal to melt and flow by capillarity between insert 3 and members 1 and 2 thereby securely attaching these members together. Sufiicient solder or brazing metal is used in attaching aluminum member 1 to insert 3 to not only bond them together but, to provide a coating 13 covering the face of insert 3 to thus prevent any contact between the copper insert 3 and the aluminum conductor which will be subsequently positioned within member 1.

Where the connector members are attached together by soldering, various conventional solders may be used, e. g. 60% tin-40% zinc or 44% tin25% zinc-3l% cadmium. Where brazing is used, various conventional brazing alloys may be utilized. For example, in brazing copper member 2 to copper insert 3 suitable alloys are 45% silver15% copper16% zinc24% cadmium and 50% silver--15.5% copper16.5% zinc--l8% cadmium. Suitable alloys for brazing copper insert 3 to aluminum member 1 are 9.3 to 10.7% silicon3.3 to 4.7% copper-0.8% iron0.2% zinc-O.15% magnesium-0.l5% manganese-0.15% chromiumbalance aluminum and 11 to 13% silicon--0.3% copper-0.8% iron0.2% zinc--0.l% magnesiurn0.l5% manganesebalance aluminum. Prior to soldering or brazing it is necessary that the assembly be suitably fiuxed. Examples of suitable fluxes are 3 to ammonium chloride97 to 90% zinc chloride and 30% sodium chloride-36% potassium chloride-8% lithium fluoridel8% lithium chloridel.9% zinc chloride-0.l% lead chloride. Such fluxes, which are generally in powder form, are mixed with a small amount of alcohol or water to provide a paste. The flux paste can be applied by any suitable means, e. g. brushing, to the rings of soldering or brazing material, to the parts to be joined, or to both. After completion of the soldering or brazing operation and prior to applicatlon of protective layer '7, any flux residue should be removed. Various procedures for flux residue removal are known, e. g. dip the attached members in a dilute solution of nitric acid (10%) and thereafter wash with hot water Figure 4 of the drawing illustrates another modificatlon ofthe connector of Figure 1 wherein the opposing end portions of members 1 and 2 are in overlapping relation and wherein a copper insert 14 having a substantially constant transverse cross-section axially thereof is utilized. Also, an aluminized coating 15 is provided on the end surface of insert 14 and member 2. In making the connector of Figure 4, it is preferable to place insert- 14 within the end of member 2, join these elements together by crimping, pressure welding, soldering or brazing, aluminize the end of insert 14 and member 2, place the end of member 2 which has been aluminized'in the end of member 1 and crimp, pressure weld, solder or 'braze members 1 and 2 together. Thereafter protective layer 7 is applied as hereinabove described. It will be understood that in place of aluminized coating 15, the member 1 may be attached to member 2 and insert 14 by means of soldering or brazing wherein sufiicient bonding metal is used to provide a coating over the end of insert 14 as shown in Figure 3 at 13. It is also to be understood that where soldering or brazing are used as means of attachment, suitable fluxing and fiux residue removal procedures are provided for as hereinabove described. In the use of the connector of Figure 4, substantially all of the current How will be from one conductor to its respective connector member, then to the second connector member and to its respective conductor.

Figure 5 of the drawing illustrates a modification of the connector of Figure 4 wherein in place of a metal insert there is provided an insert 16 of non-conducting moisture-resistant material, e. g. neoprene, which separates the space 1' in member 1 from the space 2' in member 2. Insert 16 may be provided within members 1 and 2 by any suitable means. For example, where neoprene is the material used, a suitable uncured neoprene compound may be disposed Within the members in the area of the overlap of the opposing ends, die members moved into members 1 and 2 to exert pressure against the neoprene compound, and the assembly subjected to a suitable temperature to cure and pressure mold the neoprene material in place. Prior to placement of the neoprene within the members it is desirable to provide the inner surface of the members in the area of the insert with a suitable adhesive coating 17 to ensure adherence of the insert to the members similar to the provision of outer layer 7 as hereinbefore described.

Figure 6 of the drawing illustrates a further modification wherein the insert 18 is composed of a suitable contact and sealing paste as hereinbefore described with reference to Figure 2 (number 12) of the drawing. Sufiicient contact and sealing paste is provided to not only form an effective separation between the spaces 1 and 2' of members 1 and 2, respectively, but to also form a coating on the walls thereof. Figure 7 illustrates an electrical connection between aluminum conductor 19 and copper conductor 20 utilizing the connector shown in Figure 6. In the use of connectors such as shown in Figures '5 and 6, the current how will be from one conductor to its respective connector member, through the attached second connector member and then to the conductor afiixed therein. I

It will thus be seen that by this invention there is provided an aluminum to copper connector which is simple, light and easily installed in the field with conventional tools and techniques. Also, the connector provides for effective separation of the two conductor metals with regard to their external exposed surfaces, provides a block or barrier between the internal surfaces of the two conductors, provides a high strength, low resistance attachment for current passage, and provides a permanent seal over the joint which prevents galvanic cell corrosion from occurring. Such connector makes possible an electrical connection between aluminum and copper conductors wherein the mechanical properties of the alu minum conductor and copper conductor are matched in their respective connector sides and which eliminates the problem of undesirable flow of metal. f

It will be understood that various changes and modifications may be made to the instant invention without departing from the spirit and scope thereof and, as such,

the invention is not to be taken as limited except by the appended claims, wherein what isclaimed is:

e 1. An electrical connector for joining aluminum and copper conductors in current carrying relationshipcomprising an open-ended tubular aluminum member, an open-ended tubular copper member, said members being attached together in current carrying relationship with the members positioned along the same axis, a moisture barrier insert provided within said members which completely separates the interior spaces defined by said members, and an adherent, stable, moisture-resistant and nonconducting layer provided on the external surface of said members and covering at least the exposed surface area where the members are in closest relationship.

2. An electrical connector according to claim 1 wherein the insert is metal.

3. An electrical connector according to claim 2 wherein said insert is copper and wherein the end of said insert forming one surface of the space within the aluminum member is provided with an adherent coating of a metal dissimilar to copper and aluminum.

4. An electrical connector according to claim 1 where in the insert is a moisture resistant, non-metallic material.

5. An electrical connector according to claim 1 wherein said layer possesses a shape such that the greatest thickness thereof is located intermediate the ends of said layer, which ends form the extremities of the layer along the length of the portion of the members covered by said layer.

6. An electrical connector according to claim 5 wherein said layer is hydrophobic.

7. An electrical connector according to claim 1 wherein a relatively thin non-conducting and moisture-resistant adhesive coating is interposed between said layer and the said metal surfaces aligned therewith.-

8. An electrical connector for joining aluminum and copper conductors in current carrying relationship comprising an open-ended tubular aluminum member adapted to receive therein an aluminum conductor, an open-ended tubular copper member adapted to receive therein a copper conductor, said aluminum member being larger than said copper member, said members being attached together in current carrying relationship with said members positioned along the same axis, an insert provided within said members which separates the interior spaces defined by said members from passage of moisture therethrough and from contact of the conductors to be received therein, and an adherent, stable, moisture-resistant and non-conducting layer provided on the external surface of said members and covering at least the exposed surface area where the members are in closest relationship.

9. An electrical connector according to claim 8 wherein said insert is copper, said insert comprising a reduced portion which extends into the end of said copper member and is attached thereto and an enlarged portion which extends into the end of said aluminum member and is attached thereto, the end of said insert which extends into said aluminum member being provided with a coating of a metal dissimilar to copper and aluminum.

10. An electrical connector according to claim 8 wherein said insert is copper, said insert comprising a reduced portion which extends into the end of said copper member and is attached thereto and an enlarged portion which extends into the end of said aluminum member and is attached thereto, the end of said insert which extends into said aluminum member being provided with an aluminous coating.

11. An electrical connector according to claim 8 wherein said end opposing members are in overlapped relation, said insert is copper and is secured within the end portion of said copper member and the end of said copper member and said insert forming the inner end of the space within said aluminum member is provided with a coating of a metal dissimilar to copper and aluminum.

12. An electrical connector according to claim 8 8 wherein said end opposing members are in overlapped relation and wherein said insert is composed of a mois ture-resistant, non-metallic material.

13. An electrical connection for aluminum and copper conductors comprising an aluminum conductor, a copper conductor, and a connector composed of an open-ended tubular aluminum member adapted to receive therein said aluminum conductor, an open-ended tubular copper member adapted to receive therein said copper conductor, said members being attached together in current carrying relationship, an insert provided within said members which separates the interior spaces defined by said members from passage of moisture therethrough and from contact of the conductors to be received therein, and an adherent, stable, moisture-resistant and non-conducting layer provided on the external surface of said member and covering at least the exposed surface area where the members are in closest relationship, one end of said aluminum conductor being positioned within said aluminum member and affixed thereto and one end of said copper conductor being positioned within said copper member and afiixed thereto.

14. An electrical connection according to 'claim 13 wherein said members are pressed into intimate contact with said conductors.

15. An electrical connection according to claim 14 wherein said members are indented into said conductors and wherein the space defined by said indented connector members and conductors is filled with sealing and contact material.

16. An electrical connection according to claim 13 wherein said layer possesses a shape such that the greatest thickness thereof is located intermediate the ends of said layer, which ends form the extremities of the layer along the length of the portion of the members covered by said layer. 1

17. An electrical connection according to claim 13 wherein a relatively thin non-conducting and moisture.

resistant adhesive coating is provided between said layer and said metal surface.

18. An electrical connection according to claim 13 the end portions of said end opposing members are in overlapped relation and wherein said insert is composed of a moisture-resistant, non-metallic material.

19. An electrical connection for aluminum and copper conductors comprising an aluminum conductor, a copper conductor, and a connector composed of an open-ended tubular aluminum member adapted to receive therein said aluminum conductor, an open-ended tubular copper member adapted to receive therein said copper conductor, said aluminum member being larger than said copper member, said members being attached together in current carrying relationship, a copper insert provided within said members which separates the interior spaces defined by said members from passage of moisture therethrough and from contact of the conductors to be received therein, the end of said insert forming one surface of the space within the aluminum member is provided with a coating of metal dissimilar to copper, and an adherent, stable, moisture-resistant and non-conducting layer provided on the external surface of said members and covering at least the exposed surface area where the members are in closest relationship, one end of said aluminum conductor being positioned within said aluminum member and afirxed thereto and one end of said copper conductor being positioned within said copper member and atfixed thereto.

20. An electrical connection according to claim 19 wherein said insert comprises a reduced portion which extends into the end of said copper member and is attached thereto and an enlarged portion which extends into the end of said aluminum member and is attached thereto, the end of said insert which extends into said aluminum member being provided with a coating of a metal dissimilar to copper and aluminum.

21. An electrical connection according to claim 19 wherein said insert comprises a reduced portion which extends into the end of said copper member and is attached thereto and an enlarged portion which extends into the end of said aluminum member and is attached thereto, the end of said insert which extends into said aluminum member being provided with a coating of aluminous metal.

22. An electrical connection according to claim 19 wherein the ends of said members are in overlapped relation and wherein said insert is secured within the end portion of said copper member and the end of said copper member and said insert forming the inner end of the space Within said aluminum member are provided With a coating of a metal dissimilar to copper and aluminum.

23. An electrical connector for joining aluminum and copper conductors in current carrying relationship comprising an open-ended tubular aluminum member, an open-ended tubular copper member, said members being attached together in current carrying relationship with the members positioned along the same axis, a moisture barrier insert of copper provided Within said members which completely separates the interior spaces defined by said members, the end of said insert forming one surface of the space within the aluminum member being pro vided with an adherent coating of aluminous metal, and an adherent, stable, moisture-resistant and non-conducting layer provided on the external surface of said members and covering at least the exposed surface area where the members are in closest relationship.

24. An electrical connector for joining aluminum and copper conductors in current carrying relationship comprising an open-ended tubular aluminum member adapted to receive therein an aluminum conductor, an openended tubular copper member adapted to receive therein a copper conductor, said aluminum member being larger than said copper member, said members being attached together in current carrying relationship with said members positioned along the same axis and in end over-lapping relationship, a copper insert provided within said copper member and which separates the interior spaces defined by said members from passage of moisture therethrough and from contact of the conductors to be received therein, the end of said copper member and said insert forming the inner end of the space within said aluminum member being provided with a coating of aluminous metal, and an adherent, stable, moisture-resistant and non- 10 conducting layer provided on the external surface of said members and covering at least the exposed surface area where the members are in closest relationship.

25. An electrical connection for aluminum and copper conductors comprising an aluminum conductor, a copper conductor, and a connector composed of an open-ended tubular aluminum member adapted to receive therein said aluminum conductor, an open-ended tubular copper member adapted to receive therein said copper conductor, said aluminum member being larger than said copper member, said members being attached together in current carrying relationship and with one 'end of each of said members being in over-lapping relationship, a copper insert provided Within the end portion of said copper member and which separates the interior spaces defined by said members from passage of moisture therethrough and from contact of the conductors to be received therein, the end of said copper member and said insert forming the inner end of the space Within said aluminum member being provided with a coating of aluminous material, and an adherent, stable, moisture-resistant and non-conducting layer provided on the external surface of said members and covering at least the exposed surface area Where the members are in closest relationship, one end of said aluminum conductor being positioned Within said aluminum member and aflixed thereto and one end of said copper conductor being positioned Within said copper member and ailixed thereto.

References Cited in the file of this patent UNITED STATES PATENTS 938,137 Goetz Oct. 26, 1909 1,931,309 Thompson Oct. 17, 1933 2,279,677 Heinrich Apr. 14, 1942 2,423,290 Bonwitt July 1, 1947 FOREIGN PATENTS 918,579 France Feb. 12, 1947 OTHER REFERENCES Publication I, Electrical World, November 10, 1952, pp. 32-33, 174-94.

Publication II, Electrical Engineering, May 1953, pp. 393-397, 17494.1.

Publication III, Westinghouse Engineer, May 1953, pp. 98-99, 174-94. 

13. AN ELECTRICAL CONNECTION FOR ALUMINUM AND COPPER CONDUCTORS COMPRISING AN ALUMINUM CONDUCTOR, A COPPER CONDUCTOR, AND A CONNECTOR COMPOSED OF AN OPEN-ENDED TUBULAR ALUMINUM MEMBER ADAPTED TO RECEIVE THEREIN SAID ALUMINUM CONDUCTOR, AN OPEN-ENDED TUBULAR COPPER MEMBER ADAPTED TO RECEIVE THEREIN SAID COPPER CONDUCTOR SAID MEMBERS BEING ATTACHED TOGETHER IN CURRENT CARRYING RELATIONSHIP, AN INSERT PROVIDED WITHIN SAID MEMBERS WHICH SEPARATES THE INTERIOR SPACES DEFINED BY SAID MEMBERS FROM PASSAGE OF MOISTURE THERETHROUGH AND FROM CONTACT OF THE CONDUCTORS TO BE RECEIVED THEREIN, AND AN ADHERENT, STABLE, MOISTURE-RESISTANT AND NON-CONDUCTING LAYER PROVIDED ON THE EXTERNAL SURFACE OF SAID MEMBER AND COVERING AT LEAST THE EXPOSED SURFACE AREA WHERE THE MEMBERS ARE IN CLOSEST RELATIONSHIP, ONE END OF SAID ALUMINUM CONDUCTOR BEING POSITIONED WITHIN SAID ALUMINUM MEMBER AND AFFIXED THERETO AND ONE END OF SAID COPPER CONDUCTOR BEING POSITIONED WITHIN SAID COPPER MEMBER AND AFFIXED THERETO. 